"air of impunity”

[meliss]

The last sentence doesn't make sense for me: air of impunity/ air of exemption from punishment to something - what is it?
"On June 22, 2010, a Rolling Stone article revealed his [McChrystal's] staff had been criticizing the White House. Since the surge debate, they had taken to complaining about Obama and Biden, possibly
even ridiculing the latter... McChrystal abided his staff’s offenses and hinted at his own distaste for the administration. It was a sign of disrespect for the office of the president. Realizing the gravity of his error, McChrystal resigned. Had he not, Obama would have fired him. The behavior confirmed for Obama an “air of impunity” among the generals to the principle that politicians have a duty to interfere in the running of a war."
Source: The American War in Afghanistan by Carter Malkasian

 

[Tarheel]

They somehow thought they could get away with behavior that could be considered insubordination.

 

[Ostap]

The last sentence doesn't make sense for me:

Grammatically, it doesn't to me either. But the message is clear: The behavior confirmed for Obama two things: (1) an “air of impunity” among the generals, which implies that (2) politicians have a duty to interfere in the running of a war.